Physicochemical origins of prokaryotic and eukaryotic organisms.

Abstract

Origins research currently rests on a vitalistic foundation and requires reconceptualization. From a cellular perspective, prokaryotic cells grow and divide in stable, colloidal processes, throughout which the cytoplasm remains crowded (concentrated) with closely interacting proteins and nucleic acids. Their functional stability is ensured by repulsive and attractive non-covalent forces, especially van der Waals forces, screened electrostatic forces, and hydrogen bonding (hydration and the hydrophobic effect). On average, biomacromolecules are crowded at above 15% volume fraction, surrounded by up to 3 nm layer of aqueous electrolyte at ionic strength above 0.01 molar; they are energized by biochemical reactions coupled to nutrient environments. During cellular growth, non-covalent molecular forces and biochemical reactions stabilize the cytoplasm as a two-phase, colloidal system comprising vectorially structured cytogel and dilute cytosol. From a geochemical perspective, Earth's rotation kept prebiotic molecules in continuous cyclic disequilibria in Usiglio-type intertidal pools, rich in potassium and magnesium ions, the last cations to precipitate from evaporatig seawater. These ions impart biochemical functionality to extant proteins and RNAs. The prebiotic molecules were repeatedly purified by phase separation in response to tidal drying and rewetting; they were chemically evolving as briny, carbonaceous inclusions in tidal sediments until the crowding transition allowed chemical evolution to proceeed toward Woesian progenotes, the Last Universal Common Ancestors (LUCAs) and the first prokaryotes. These cellular and geochemical processes are summarized as a jigsaw puzzle of the emerging and evolving prokaryotes. Their unavoidable cyclic fusions and rehydrations along Archaean coastlines initiated the emergence of complex Precambrian eukaryotes.